Both eukaryotic and prokaryotic cells respond to mild temperature elevation (and many other forms of stress) by inducing the synthesis of a small group of highly conserved proteins called the heat-shock proteins (HSPs). A good deal of indirect evidence suggests that these proteins provide protection from the toxic effects of heat, but little is known about their specific molecular functions. Recent work has shown that some of these proteins are induced during the normal course of development, suggesting they may also play important roles in normal cellular processes. We wish to investigate the heat-shock response of the yeast, Saccharomyces cerevisiae, because this organism offers so many unique advantages for genetic manipulation. We are in the process of creating mutations in several of the yeast heat-shock genes and producing antibodies specific for the proteins. These mutants and antibodies will be used as tools to study the function and regulation of the proteins during normal growth, sporulation and exposure to stress.